Over recent years, composite materials have become an increasingly desirable material for aircraft structures. Composite materials typically comprise strands of fibers (e.g., glass- and/or carbon-fiber) mixed with a resin. For example, many commercially produced composites use a polymer matrix material as the resin. Common composite materials used on airplanes include fiberglass, carbon fiber, and fiber-reinforced matrix systems, or any combination of any of these. In fact, there are many different polymers available, depending upon the starting raw ingredients. The more common polymer may include, for example, polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene, and PEEK. During fabrication, fibers may be often wound, or woven, into a sheet of material and then impregnated (e.g., infused) with a resin. Once the fibers have been impregnated with a resin, the composite material may then be formed into the desired shape and cured until properly hardened.
Composite materials have an advantage of being extremely lightweight and having high strength. As a result, they are useful in, among other things, aircraft applications. Additionally, composite structures may be molded into desired shapes and configurations. While many parts manufactured using composite materials could also be made from metal, a metallic part of the same strength and stiffness would be significantly heavier.
However, manufacturing components using composite materials can be time-consuming and labor intensive, especially when complex structures are needed. An additional drawback of certain composite materials is the actual assembly, or joining, of the composite materials. Unlike more traditional materials (e.g., metals), different considerations must be made for assembling composite materials. For example, placing holes in composite materials for attachment of fasteners severs the strands of fibers within the material and creates weak points within the material. While forming holes in the composite material by displacing the strands of the uncured fibers prevents severing of the fibers, this process is time-consuming and often impractical. Another alternative for assembling composite materials is the use of high-strength epoxies. Epoxies have an advantage of limiting the number of manufacturing steps. However, the distribution of the epoxy and the placement of the parts together can require expensive machines and numerous jigs (e.g., tooling). Moreover, such structures routinely involve multiple sets of tools, are very labor intensive, require several cure cycles and can require B-staged material with set expiration dates.
Additive manufacturing techniques, i.e., 3-D printing, are beneficial to traditional composite material manufacturing techniques in that they provide the ability to rapidly produce and iterate printed polymeric components at reduced cost and time in comparison to composite material manufacturing techniques. Additive manufacturing processes also allow implementation of unique features into the printed component, which are difficult to produce using composite manufacturing methods. However, it is difficult for polymers to match the mechanical performance of composite materials. As a result, polymers are often not viable materials for large-scale use in constructing aircraft components.
Accordingly, there is a need in the art, for a method of manufacturing structures that leveraging the benefits of composite materials and additive manufactured components, while alleviating the drawbacks discussed above.